The present invention concerns automatic closing devices, such as for example automatic window lifters and roof closing systems in a motor vehicle that is fitted with a pinch protection function and that can be switched off and switched on again by automatic vehicle functions.
As a rule, automatic closing devices comprise a closing element (window pane, sliding roof) that is electrically driven by an electric motor. The electric motor is actuated by a control unit that is coupled to an operating element in order to actuate the electric motor depending on operation of the operating element and to specify the direction of motion of the electric motor.
In the case of closing devices on a motor vehicle, such as for example electric window lifters, electric sliding roofs and similar, it must be ensured that there are no objects or body parts that can be damaged or injured during a closing process, during which the closing element is moved toward a stop edge (window frame, roof opening). In order to avoid such a case, an algorithm is implemented in a control unit that detects a case of pinching during a closing process of the closing element. If a case of pinching is detected, the closing process is stopped, or reversing is carried out, during which the closing element at least briefly performs an opening movement.
The closing device is activated using the operating element as a rule, and an automatic operation can be activated depending on the type of operation of the operating element, during which the closing element is automatically moved in the opening direction or in the closing direction without the operating element having to remain operated. In an automatic operation mode the automatic operation can for example be activated when operating the operating element for a certain period of time.
In order to implement switching off of the electric motor on detecting pinching, as a rule a measurement variable is analyzed in order to obtain an indicator that is proportional to the pinching force. For example, in the case of electric closing devices a revolution rate gradient is often analyzed for this purpose, and pinching of a body part or an object between the stop edge and the closing element can be detected depending on a measurement variable determined from the profile of the revolution rate gradient. The magnitude of the measurement variable is available as an indication of a pinching force being present. If the measurement variable exceeds a specified pinching force threshold value in magnitude, then the electric motor is stopped and reversed in order to cause an opening movement of the window pane and to release any pinched body part or object.
It is the object of the present invention to provide a more reliable pinch protection function for a closing device, with which in particular exceeding a maximum pinching force can be avoided following the start of a closing process of a closing device.